A tsunami can be
generated by any disturbance that displaces a large mass of water, such as an
earthquake, landslide or meteor impact.
Tsunamis can be
generated when the sea floor abruptly deforms and vertically displaces the
overlying water. Tectonic earthquakes are a particular kind of earthquake that
are associated with the earth's crust deformation; when these earthquakes occur
beneath the sea, the water above the deformed area is displaced from its
equilibrium position.
Waves are formed as
the displaced water mass moves under the influence of gravity to regain its
equilibrium. When large areas of the sea floor elevate or subside, a tsunami
can be created. Large vertical movements of the earth's crust can occur at
plate boundaries. Plates interact along these boundaries called
"faults". Around the margins of the Pacific Ocean, for example,
denser oceanic plates slip under continental plates in a process known as
subduction. Subduction earthquakes are particularly effective in generating
tsunamis.
Submarine landslides,
which often accompany large earthquakes, as well as collapses of volcanic
edifices, can also disturb the overlying water column as sediment and rock
slump downslope and are redistributed across the sea floor. Similarly, a
violent submarine volcanic eruption can uplift a water column and generate a
tsunami.
Large landslides and
cosmic-body impacts can disturb the water from above, as momentum from falling
debris is transferred to the water into which the debris falls. Generally
speaking, tsunamis generated from these mechanisms, unlike the Pacific-wide
tsunamis caused by some earthquakes, dissipate quickly and rarely affect
coastlines distant from the source area. However if the landslide or cosmic
body is large enough, it will create a megatsunami. A megatsunami is a tsunami,
usually caused by a collapsing island, asteroid impact, or huge chunks of ice
falling into a large body of water, and is hundreds of meters high.font:
iem/seed/pr
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